boot from ZFS: which pool types use?

[Kimmo Paasiala]

On Thu, Jul 4, 2013 at 1:42 PM, Dmitry Morozovsky <marck at rinet.ru> wrote:
> Dear colleagues,
>
> I'm a bit stuck and possibly my google-fu sleeps somewhere, but I have
> inconsistent cases on what pool types can one use to boot contemporary
> (read: stable/9) FreeBSD from.
>
> For example, I have many older servers with UFS /bootdisk and ZFS-on-root.
> While this is useable, it does not seem to be very consistent.
>
> On the other hand, I have a couple of servers with ZFS-only config which uses
> complex raid10-like config on gpart disks, and they boot flawlessly, at lest
> till now.
>
> Lastly, I'm now in process of setting up new server, and trying to do the same,
> configuring ZFS with 4 pairs of SAS, now have
>
> Can't find /boot/zfsloader
>
> I suppose from line 619 from sys/boot/i386/zfsboot/zfsboot.c
>
> Configs are essentially the same, I double-check gpart bootcode and zpool.cache
> (while I still did not found the guide how to interprete its content; at least
> one of my ZFS servers successfully runs without it)
>
> Any hints?  Are stripe-mirror configuration available for booting from (yes, I
> do remember that all, or at last enough for degraded use, disks should be
> exposed to BIOS by controller firmware, and it is usually constrained to 6 or 8
> disk devices)
>
> Thanks!
>
>
> --
> Sincerely,
> D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
> [ FreeBSD committer:                                 marck at FreeBSD.org ]
> ------------------------------------------------------------------------
> *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
> ------------------------------------------------------------------------
> _______________________________________________

I no longer have my FreeBSD 9-STABLE fileserver but I was booting
succesfully from a four disk striped mirror ZFS pool (two 2-disk
mirror vdevs in other words) that was pure ZFS, no UFS /boot involved.
It always worked like a charm.

-Kimmo